[PATCH 0/1] s390/dasd: fix kernel panic due to missing discipline function

[PATCH 0/1] s390/dasd: fix kernel panic due to missing discipline function

[Stefan Haberland]

Hi Jens,

please apply the following patch that fixes a kernel panic in the DASD
device driver.

Stefan Haberland (1):
  s390/dasd: add missing discipline function

 drivers/s390/block/dasd_diag.c | 8 +++++++-
 drivers/s390/block/dasd_fba.c  | 8 +++++++-
 drivers/s390/block/dasd_int.h  | 1 -
 3 files changed, 14 insertions(+), 3 deletions(-)

-- 
2.25.1

[PATCH 1/1] s390/dasd: add missing discipline function

[Stefan Haberland]

Fix crash with illegal operation exception in dasd_device_tasklet.
Commit b72949328869 ("s390/dasd: Prepare for additional path event handling")
renamed the verify_path function for ECKD but not for FBA and DIAG.
This leads to a panic when the path verification function is called for a
FBA or DIAG device.

Fix by defining a wrapper function for dasd_generic_verify_path().

Fixes: b72949328869 ("s390/dasd: Prepare for additional path event handling")

Cc: <stable@vger.kernel.org> #5.11
Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
---
 drivers/s390/block/dasd_diag.c | 8 +++++++-
 drivers/s390/block/dasd_fba.c  | 8 +++++++-
 drivers/s390/block/dasd_int.h  | 1 -
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/block/dasd_diag.c b/drivers/s390/block/dasd_diag.c
index 1b9e1442e6a5..fd42a5fffaed 100644
--- a/drivers/s390/block/dasd_diag.c
+++ b/drivers/s390/block/dasd_diag.c
@@ -642,12 +642,18 @@ static void dasd_diag_setup_blk_queue(struct dasd_block *block)
 	blk_queue_segment_boundary(q, PAGE_SIZE - 1);
 }
 
+static int dasd_diag_pe_handler(struct dasd_device *device,
+				__u8 tbvpm, __u8 fcsecpm)
+{
+	return dasd_generic_verify_path(device, tbvpm);
+}
+
 static struct dasd_discipline dasd_diag_discipline = {
 	.owner = THIS_MODULE,
 	.name = "DIAG",
 	.ebcname = "DIAG",
 	.check_device = dasd_diag_check_device,
-	.verify_path = dasd_generic_verify_path,
+	.pe_handler = dasd_diag_pe_handler,
 	.fill_geometry = dasd_diag_fill_geometry,
 	.setup_blk_queue = dasd_diag_setup_blk_queue,
 	.start_IO = dasd_start_diag,
diff --git a/drivers/s390/block/dasd_fba.c b/drivers/s390/block/dasd_fba.c
index 4789410885e4..3ad319aee51e 100644
--- a/drivers/s390/block/dasd_fba.c
+++ b/drivers/s390/block/dasd_fba.c
@@ -794,13 +794,19 @@ static void dasd_fba_setup_blk_queue(struct dasd_block *block)
 	blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
 }
 
+static int dasd_fba_pe_handler(struct dasd_device *device,
+			       __u8 tbvpm, __u8 fcsecpm)
+{
+	return dasd_generic_verify_path(device, tbvpm);
+}
+
 static struct dasd_discipline dasd_fba_discipline = {
 	.owner = THIS_MODULE,
 	.name = "FBA ",
 	.ebcname = "FBA ",
 	.check_device = dasd_fba_check_characteristics,
 	.do_analysis = dasd_fba_do_analysis,
-	.verify_path = dasd_generic_verify_path,
+	.pe_handler = dasd_fba_pe_handler,
 	.setup_blk_queue = dasd_fba_setup_blk_queue,
 	.fill_geometry = dasd_fba_fill_geometry,
 	.start_IO = dasd_start_IO,
diff --git a/drivers/s390/block/dasd_int.h b/drivers/s390/block/dasd_int.h
index 1c59b0e86a9f..155428bfed8a 100644
--- a/drivers/s390/block/dasd_int.h
+++ b/drivers/s390/block/dasd_int.h
@@ -297,7 +297,6 @@ struct dasd_discipline {
 	 * e.g. verify that new path is compatible with the current
 	 * configuration.
 	 */
-	int (*verify_path)(struct dasd_device *, __u8);
 	int (*pe_handler)(struct dasd_device *, __u8, __u8);
 
 	/*
-- 
2.25.1

Re: [PATCH 1/1] s390/dasd: add missing discipline function

[Cornelia Huck]

On Tue, 25 May 2021 14:50:06 +0200
Stefan Haberland <sth@linux.ibm.com> wrote:

> Fix crash with illegal operation exception in dasd_device_tasklet.
> Commit b72949328869 ("s390/dasd: Prepare for additional path event handling")
> renamed the verify_path function for ECKD but not for FBA and DIAG.
> This leads to a panic when the path verification function is called for a
> FBA or DIAG device.
> 
> Fix by defining a wrapper function for dasd_generic_verify_path().
> 
> Fixes: b72949328869 ("s390/dasd: Prepare for additional path event handling")
> 
> Cc: <stable@vger.kernel.org> #5.11
> Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
> Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
> ---
>  drivers/s390/block/dasd_diag.c | 8 +++++++-
>  drivers/s390/block/dasd_fba.c  | 8 +++++++-
>  drivers/s390/block/dasd_int.h  | 1 -
>  3 files changed, 14 insertions(+), 3 deletions(-)

Oops.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

[Just to satisfy my curiosity: are there still any FBA devices around,
other than z/VM emulating a DASD frontend for FCP devices?]

Re: [PATCH 0/1] s390/dasd: fix kernel panic due to missing discipline function

[Jens Axboe]

On 5/25/21 6:50 AM, Stefan Haberland wrote:
> Hi Jens,
> 
> please apply the following patch that fixes a kernel panic in the DASD
> device driver.
> 
> Stefan Haberland (1):
>   s390/dasd: add missing discipline function
> 
>  drivers/s390/block/dasd_diag.c | 8 +++++++-
>  drivers/s390/block/dasd_fba.c  | 8 +++++++-
>  drivers/s390/block/dasd_int.h  | 1 -
>  3 files changed, 14 insertions(+), 3 deletions(-)

Applied, thanks.

-- 
Jens Axboe

Re: [PATCH 1/1] s390/dasd: add missing discipline function

[Stefan Haberland]

> [Just to satisfy my curiosity: are there still any FBA devices around,
> other than z/VM emulating a DASD frontend for FCP devices?]
>

Currently no, only emulated ones. So there are likely no "real" path
events for the virtual devices and the bug would not be triggered in the
wild.
But one could accidentally trigger it by explicitly doing a "chchp -v 1"
on the virtual path.